1. Field of the Invention
The present invention relates to image display apparatuses and methods, programs therefor, and recording media having recorded thereon the same, which can be applied to, for example, a monitor including a liquid crystal display (LCD) panel in which the coloring of an edge or the like is prevented by correcting the phases of pieces of color data on the basis of the arrangement (positions) of subpixels in each pixel, and the signal levels of the pieces of color data are corrected so as to correct the luminance levels of the subpixels, which change depending on the viewing direction, thereby preventing the coloring of the edge or the like by correcting the phases of the pieces of color data on the basis of the arrangement (positions) of the subpixels in each pixel while preventing a change in the luminance level of each subpixel depending on the viewing direction.
2. Description of the Related Art
In flat displays of the related art including LCDs and plasma display panels (PDPs), each pixel includes a plurality of subpixels of different colors, which are driven by associated pieces of color data to display a desired image.
That is, as shown in FIG. 8, a display device 1 of this type includes red subpixels 2R, green subpixels 2G, and blue subpixels 2B, which are sequentially and recursively arranged in the horizontal direction. Three consecutive subpixels 2R, 2G, and 2B form one pixel 3.
With regard to such a display device, a method has been proposed in, for example, Japanese Unexamined Patent Application Publication 2003-259386. The method involves correcting the phases of pieces of color data to be supplied to drive the associated subpixels on the basis of the arrangement (positions) of the subpixels, thereby increasing the apparent resolution.
In this type of display device, in the case where the subpixels are simply driven by the associated pieces of color data, when gray is displayed, an edge portion and a portion where the luminance gradually changes in gradation or the like seem to be colored.
That is, each piece of color data is a sampling value obtained at a timing for scanning the center of each pixel by raster scanning. Accordingly, as shown in FIG. 9A, in an edge portion in the case where gray is displayed, the luminance levels of three subpixels 2R, 2G, and 2B included in one pixel are reduced at the same time. Therefore, in this case, the color of a subpixel 2B1 which is the most adjacent to the edge and whose luminance level is high becomes striking in the edge portion, and hence, the edge portion seems to be colored with the color of the subpixel 2B1. In FIGS. 9A to 9D, the luminance levels of the subpixels 2R, 2G, and 2B are indicated in a height direction.
At the same time, as shown in FIG. 9B, in a portion where the luminance level gradually changes in the case where gray is displayed, the luminance levels of three subpixels 2R, 2G, and 2B included in one pixel are sequentially reduced step by step. Therefore, in this case, the color of the subpixel 2B on the side where the luminance level is gradually reduced becomes striking, and the portion where the luminance level gradually changes seems to be colored with the color of the subpixel 2B.
In order to solve these problems, one method involves correcting the phases of pieces of color data to be supplied to drive the subpixels 2R, 2G, and 2B on the basis of the arrangement (positions) of the subpixels 2R, 2G, and 2B in each pixel 3.
That is, as shown in FIGS. 9C and 9D in contrast to FIGS. 9A and 9B, in the case where the red, green, and blue subpixels 2R, 2G, and 2B are sequentially and recursively arranged, and the three consecutive red, green, and blue subpixels 2R, 2G, and 2B form one pixel 3, the subpixel 2G at the center of the pixel 3 is driven in a manner similar to the related art. With regard to the subpixel 2R prior to the central subpixel 2G, the phase of the associated piece of color data is corrected for the preceding portion, and the subpixel 2R is driven using the phase-corrected color data. In contrast, with regard to the subpixel 2B subsequent to the central subpixel 2G, the phase of the associated piece of color data is corrected for the portion subsequent to the subpixel 2G, and the subpixel 2B is driven using the phase-corrected color data.
Accordingly, in the edge portion, the luminance levels of the subsequent subpixel 2B and the preceding subpixel 2R subsequent to this subpixel 2B are sequentially reduced step by step, thereby preventing the coloring of the edge portion. In the portion where the luminance level gradually changes in gradation or the like, the luminance levels of the subpixels 2R, 2G, and 2B are sequentially reduced so as to correspond to the reduction in the luminance level, thereby preventing the coloring of this portion.
However, in this type of display device, as in a twisted nematic (TW) liquid crystal by way of example, luminance characteristics change depending on the viewing direction, and, as a result, the luminance level of each subpixel changes depending on the viewing direction. In the case where the luminance level of each subpixel changes depending on the viewing direction, when the phases of pieces of color data are corrected on the basis of the arrangement (positions) of the subpixels 2R, 2G, and 2B in each pixel 3 in the above-described manner, the color changes depending on the viewing direction in a repeated-pattern portion where the spatial frequency is high.
That is, as shown in FIGS. 10A and 10B in contrast to FIGS. 9A to 9D, in the case where the luminance levels of the subpixels 2R, 2G, and 2B included in each pixel 3 are maintained at the same level, and the luminance level changes in units of pixels, the luminance level ratio among the subpixels 2R, 2G, and 2B in each pixel 3 does not change between the case shown in FIG. 10A when viewed from the front and the case shown in FIG. 10B when viewed diagonally. In this case, the color does not change when the viewing direction changes.
However, as shown in FIGS. 10C and 10D in contrast to FIGS. 10A and 10B, when the phases of pieces of color data are corrected on the basis of the arrangement (positions) of the subpixels 2R, 2G, and 2B, the luminance level ratio among the subpixels 2R, 2G, and 2B in each pixel 3 changes between the case when viewed from the front and the case when viewed diagonally. Therefore, in this case, the color changes depending on the viewing direction. When the driving of the subpixels 2R, 2G, and 2B is adjusted so as to achieve the color balance when viewed from the front, the color balance when viewed diagonally is disrupted.
In this type of display device, the luminance level of each subpixel may change depending on the viewing direction due to the effects of the refractive index and the transmittance of a panel surface material, such as glass, provided on the surface of a display screen.